I'm configuring 2.6.3 for my U60. It all works fine, except the keyboard and mouse. Yes, I have changed the KEYMAP in rc.conf, but that is not the problem. I haven't got input at all. I can't even turn the numlock light on.
I have a standard sun5u keyboard and a standard serial sun mouse attached to the keyboard. The keyboard is connected with a 8 pin din connector to my u60.
When I boot to 2.4.23 it works fine.

As far as I know there are only 2 kernel options that need to be enabled:
- CONFIG_KEYBOARD_SUNKBD=y
- CONFIG_MOUSE_SERIAL=y

dmesg tells me absolutely nothing about a keyboard. The only message about the mouse is:
mice: PS/2 mouse device common for all mice

Make sure you have Sun SU serial support enabled in addition to Sun Siemens SAB82532 serial support. SU serial is the keyboard and mouse where Siemens is the serial ports on the back of the machine itself. Got nailed by this on a U5.